In an attempt to understand brain function further both in normal man and in disease states, specific aspects of the electroencephalogram (EEG) and related electrophysiological signals are analyzed in the context of "signals in a communications system". For the analyses of the electrophysiological data, several techniques, drawn in part from statistical communication theory, are employed. In a hybrid analog- digital arrangement, these include autocorrelation, crosscorrelation, electronic averaging (a simplified form of crosscorrelation), frequency analysis (power density spectrum analysis), and several techniques of digital filtering. Physiological problems under investigation include the following: (1) interhemispheric relationships of the normal and abnormal EEG and the interrelationship of intrinsic rhythmic EEG activity and that induced by rhythmic visual stimulation; (2) the mechanisms of operation of the eye (sensory receptor)-brain-eye (motor organ) as an integrated functional unit for the receipt and processing of complex visual information; (3) exploration of several digital computer techniques of evaluation of clinical EEGs, with an eventual view towards automatic computer interpretation and reporting of the clinical EEG; (4) the continued development of instrumentation and computer programs for the processing and display of electrophysiological and related signals, as well as for such signals simulated electronically, in order to test data-processing techniques and of new hypotheses suggested by the results of physiological experiments.